In existing imaging apparatuses such as digital cameras, there is a method of horizontally sliding the camera with respect to a subject to be photographed (subject) and photographing a panoramic or 3D (stereo) picture. In this photographing method, usually a few pictures are photographed automatically or manually during the slide. In general, a desired image is obtained by, in the case of a panoramic picture, stitching the photographed pictures in the slide direction, or in the case of a 3D (stereo) picture, extracting appropriate two pictures or generating a 3D picture based on the photographed pictures. Since such a generation method is well known, the details will not be provided here.
Such photographing is explained. FIGS. 7A to 7E show examples of panoramic photographing using an imaging apparatus of a related art. As shown in FIG. 7A, several images are photographed while sliding the camera horizontally, and photographed images 71 to 74 are stitched thereby to generate one panoramic picture as shown in FIG. 7B. Moreover, as shown in FIG. 7C, in a similar manner, several pictures are photographed during the slide to photograph images 75 to 80. Then, as shown in FIGS. 7D and 7E, a 3D (stereo) picture may be created by generating two pictures with disparities based on information of the images 75 to 80.
In both cases of photography, in order to generate a rectangular picture based on the photographed several pictures, it is necessary to detect correlated portions in the photographed several pictures and use the correlated portions as overlapping portions upon combining pictures. However, the camera may shake in the up-and-down direction and rotation direction with respect to the subject because the pictures are photographed while sliding the camera horizontally. The greater the camera shakes, the lower the correlation between the photographed several pictures, specifically, the overlapping portions will be smaller, thereby influencing quality and size of a resultant picture.
An example of the influence generated by the camera shake is explained. FIGS. 8A to 8D explain the camera shakes. FIGS. 8A to 8D explain the camera shakes using panoramic photographing as an example. As shown in FIGS. 8A to 8D, in this example, one panoramic picture is obtained from four pictures. FIG. 8A shows pictures with small camera shakes, while FIG. 8C shows an example with large camera shakes. In the pictures shown in FIG. 8A, images 81 to 84 have strong correlations between the photographed several pictures as the camera shakes in the up-and-down direction with respect to the subject are small, and consequently, it is possible to extract a panoramic picture with the size in the up-and-down direction (vertical direction of the screen) mostly remaining the same, as shown in FIG. 8B.
On the other hand, in the pictures shown in FIG. 8C, images 85 to 88 have weak correlations between the photographed several pictures as the camera shakes in the up-and-down direction with respect to the subject are large. Thus as shown in FIG. 8D, only a panoramic picture with a small size in the up-and-down direction (vertical direction of the screen) can be extracted with less amount of information and more deteriorated photograph quality than the panoramic picture of FIG. 8B.
In FIGS. 8A to 8D, the panoramic photographing is used as an example, however also in 3D (stereo) photographing in which the camera horizontally slides to photograph images, the correlations between several pictures photographed in a similar manner are greatly associated with quality of a final picture obtained eventually.
Therefore, some imaging apparatuses of related arts display a photographing guide to guide a user upon photographing an image. For example, patent literature 1 discloses a method of photographing several pictures while sliding the camera and stitching the pictures to obtain a panoramic picture. Patent literature 1 also suggests a function of drawing, on a screen, a vertical line for guide as an indication of a composite point to be combined with a previously photographed image. Patent literature 2 discloses a similar technique as well. However, there is a problem in these methods in which a photographer is forced to compare a shape of a subject in order to prevent displacement between the previously photographed picture and a picture to be photographed, and it is thus difficult to photograph the image without displacement depending on the subject.
Further, the technique disclosed in patent literature 3 displays, after a first picture is photographed, a pointer as a movement mark that moves according to an amount of image movement determined as a result of motion detection processing performed by a motion detection unit and a target as a movement target mark indicating a movement target position for the pointer. Specifically, a next photographing position is determined such that a predetermined range of partial images overlaps. Patent literature 3 discloses a technique of setting the pointer and the movement target position (target position) of the pointer according to the next photographing position and placing the pointer and the target over a live view image to move the pointer over the target, thereby promoting a panning operation.
Furthermore, patent literature 4 discloses a technique of displaying a pair of guide marks, which is composed of a movement mark indicating a relative position of a camera to a subject and a goal mark indicating a target position for the movement mark to move and reach. Then, a target mark Tm of the guide marks is an index and the movement mark that moves on a monitor screen of a display along with a movement of a camera by a user and indicates a relative position of a camera 1 to the subject. A goal mark Gm is a target position to which the user moves and lets the target mark Tm (movement mark) reach by moving the camera on the monitor screen of the display and is an appropriate position for photographing a panoramic picture. These displayed marks are guides for the user.